问题补充:
— It be Jack who is in the office.
— No, it be him. I saw him off at the airport half an hour ago.
A. can’t ; can’t
B. must; can’t
C. must; mustn’t
D. may; mustn’t
答案:
A. can’t ; can’t
(答案→)B. must; can’t
C. must; mustn’t
D. may; mustn’t
解析:must表推测只用于肯定句;在否定句和疑问句中用can。